A number of stereoscopic imaging and/or viewing arrangements are known. For example GB 606,065, which dates from 1948, discloses an arrangement for viewing scale models in stereoscopic fashion wherein a viewing tube containing an objective lens and a further lens is combined with two mutually orthogonal mirrors which divert light exiting from left and right regions of the further lens to respective eyepieces of a binocular viewing arrangement. Also U.S. Pat. No. 2,639,653, which dates from 1949, discloses a camera arrangement for taking microphotographs using a microscope, the pictures can then be viewed through a stereoscope to give a three-dimensional impression of the object. Accordingly, the fundamental optics involved in making stereoscopic images is well-known. However, applying these stereoscopic techniques to conventional optical devices such as microscopes and endoscopes in a manner that allows for the easy capture of both still and video images is significantly more complicated, and has not met with as much success as might have been expected given the time and effort devoted to these technologies.
For example, modern research microscopes frequently incorporate beam-splitting assemblies to permit additional viewing, video, and camera attachment ports. Available beam splitters come in a wide variety of configurations and can provide one or more optical attachment ports in addition to the primary viewing eyepieces. In addition, to provide even greater flexibility, some adapters are designed to permit the attachment of more than one camera to a single optical port on a microscope beam splitter. Adapters for simultaneously mounting a video camera and a 35-mm camera on one side of a surgical microscope beam splitter are shown, for example, in U.S. Pat. Nos. 4,272,161 and 4,143,938, the disclosures of which are incorporated herein by reference. Such adapters are commercially available from Carl Zeiss, Inc., and manufactured by Urban Engineering Co., Burbank, Calif.
Other prior art references describe other optical adapters that allow for the integration of video cameras, the use of automatic iris control, the integration of zoom, and the change in magnification into these optical attachments. For example, beam Splitters having integral video cameras are shown in U.S. Pat. Nos. 4,805,027 and 4,344,667; a beam splitter having three identical optical trains and four viewing stations is shown in U.S. Pat. No. 4,688,907; automatic iris control systems for use with surgical microscope adapters are shown in U.S. Pat. Nos. 3,820,882 and 4,300,167; A zoom lens adapter for an endoscopic camera is shown in U.S. Pat. No. 4,781,448; and a universal adapter that allows for the use of different focal length magnifications are shown in U.S. Pat. No. 5,264,928, the disclosures of each of which are incorporated herein by reference.
While functional and useful, such microscopic adapters generally only allow for the recording or projection of non-stereoscopic images. A recent advance in microscopy is the addition of stereoscopic imaging devices that allow for recordation of projection of stereoscopic images. The usual microscope contains a single objective lens, which functions to produce a magnified image of the subject to be viewed, and either a single ocular for viewing with a single eye, dual oculars for viewing with right and left eyes, or an access hole for recording magnified images with a still or video camera. Most of these conventional adapters only allow for observation through one optical path of the objective lens so the viewer has had no perception of depth. To address this limitation, some adapters, particularly for those used in surgical applications, have been modified to allow for stereoscopic viewing. However, most of these adapters require the use of multiple objective lenses at different optical axes, such as the device disclosed in U.S. Pub. No. 2002/0080481, or the use of a single camera that is designed to take images from multiple optical axes, such as that disclosed in U.S. Pat. No. 3,574,295, the disclosures of each of which are incorporated herein by reference. Unfortunately, any such multi-camera device is extremely complicated and expensive to produce.
Single lens stereoscopic microscopic ocular adapters have been proposed, however, to date the devices have had serious drawbacks. One class of such single lens stereoscopic microscope adapters require the use of polarizers or filters, however, such devices have been known to reduce the optical quality of the image, and often require that the viewer maintain a particular viewing angle with respect to the image. Either required polarizers or filters, both of which have significant drawbacks. Examples of such devices are provided in U.S. Pat. Nos. 3,712,199; 4,716,066; 5,835,264; 5,867,312; and 6,275,335 the disclosures of which are incorporated herein by reference. Other alternative methods require the use of active shutters, which are more costly to install, more difficult to maintain, and, when it fails, significantly degrades the optical properties of the lens. Such methods are disclosed, for example, in U.S. Pat. Nos. 5,471,237; 5,617,007; and 5,828,487, the disclosures of which are incorporated herein by reference.
Likewise, more recently stereoscopic endoscopes have been developed. In view or the size constraints on an endoscope, it is highly desirable to minimize the transverse dimensions of the optical system and for this reason many designs utilize a single objective and a beam splitting arrangement in its optical path which separates the light forming the left and right images. For example U.S. Pat. No. 5,222,477 discloses a stereoscopic endoscope arrangement wherein an aperture plate is located adjacent the objective lens of a video camera assembly in the distal tip of the endoscope. Left and right apertures of the plate are opened alternately by a shutter which is coupled to a video switching arrangement. In this manner left and right images are detected in rapid succession and are alternately displayed on a monitor screen so that they can be viewed stereoscopically by means of a pair of spectacles in which the left and right eyepieces are occluded alternately in rapid succession in synchronism with the display. Such display systems are commercially available. However the shutter arrangement has the disadvantage that it cannot easily be retrofitted to an existing monocular endoscope. Furthermore the addition of shutter components to the tip portion of the endoscope tends to increase its bulk, which is undesirable.
The provision of a beam splitting arrangement at the exit pupil of the endoscope in accordance with GB-A-2,268,283 avoids some of the above-noted problems of the arrangement of U.S. Pat. No. 5,222,477 but requires precise arrangement of the optical axis of the beam splitter with the optical axis of the endoscope and also requires that the rays exiting from the ocular of the endoscope are parallel. Furthermore the provision of a beam-splitting arrangement undesirably increases the number of reflecting surfaces and adds to the expense of the apparatus.
One solution to the persistent problem of producing a stereoscopic image from a single lens in these devices is set forth by Watts in U.S. Pat. No. 5,914,810, which splits the lens into three offset segments in a single simple shutter element. (The disclosure of the Watts patent is incorporated herein by reference. Although the Watts technology appears to offer a promising solution to single lens stereoscopic imaging, to date no attempt has been made to integrate the technology into surgical microscopes or endoscopes.
Accordingly, it would be advantageous to develop an optic adapter capable of allowing for the projection or recordation of stereoscopic images from single lens standard optical devices such as microscopes and endoscopes using a simple passive “optical shutter” that allows for the use of the entire functionality of the underlying optical device including variable magnifications.